1. Field of the Invention
The present invention relates to providing call backup of a Voice over Internet Protocol (VoIP) terminal and, more particularly, the present invention relates to providing call backup of a VoIP terminal, where a Public Switched Telephone Network (PSTN) backup function of the VoIP terminal connected to a VoIP network is enhanced so that better service can be provided to users.
2. Description of the Related Art In a VoIP network providing a general PSTN backup function, a VoIP mode of a telephone connected to the VoIP terminal is first set.
Next, the VoIP terminal determines whether or not a mode selection signal has been received from the telephone by selecting a specific button of the telephone set by a user.
The specific button is defined in a configuration file downloaded from the OSS when the VoIP terminal is connected to the VoIP network.
As a result of the determination, the VoIP terminal operates a relay switch to directly connect the telephone to the Switching Center through the PSTN to set the PSTN mode when the mode selection signal has been received from the telephone.
The Switching Center determines whether or not an incoming signal in accordance with the user's selection has been transmitted from the telephone. When the incoming signal has been received, the Switching Center identifies an incoming phone terminal and connects a call to effect voice communication between the corresponding incoming telephone terminal and the telephone connected to the VoIP terminal.
The VoIP terminal determines whether or not the telephone or the incoming telephone terminal is on the hook when the user hangs up, and sets the VoIP mode in which the telephone is connected to the VoIP network when the VoIP terminal is on the hook.
However, the above-noted method where the VoIP terminal provides the PSTN back up function has the following problems.
Firstly, the user cannot be automatically provided with the information message service and urgent communication service from the Switching Center through the telephone connected to the VoIP terminal.
That is, the VoIP terminal operates the relay switch and connects the telephone to the Switching Center only when the user selects a specific button and a mode selection signal is transmitted from the telephone.
When the VoIP terminal connects the telephone to the Switching Center, the Switching Center recognizes that the telephone is off the hook and transmits a dial tone.
Accordingly, there are problems in that the user has to listen for the dial tone transmitted from the Switching Center, again select a button which is used to request the information message service or the urgent communication service, and retransmit the request signal to the Switching Center.
Secondly, there is no function provided where the on the hook state is deferred for a predetermined time period in case an unexpected problem broke out while an urgent call requested by the user is made so that it is mandatory that the telephone be on the hook.
For example, it is required that even though the user necessarily leaves the telephone on the hook due to an unexpected reason while the user makes an urgent call, for example, a crime report, the VoIP terminal defers the on the hook state for a predetermined time period so that the Switching Center or the incoming party can grasp the state of the user. However, conventional methods did not consider the above.
Thirdly, the VoIP terminal cannot detect a ring tone signal transmitted from the Switching Center while the VoIP mode is set where the telephone is connected to the VoIP network.
Accordingly, there is a problem that the PSTN line cannot be used while the VoIP is setting the VoIP mode.
Finally, in the PSTN mode where the VoIP terminal connects the telephone 91 to the PSTN in accordance with the user's selection, it is not possible to sense a state of the usage of the telephone, that is, the on the hook or off the hook state of the telephone.
The following patents each discloses features in common with the present invention but do not teach or suggest the inventive features specifically recited in the present application: U.S. Patent Application No. 2004/0022237 to Ellliott et al., entitled VOICE OVER DATA TELECOMMUNICATIONS NETWORK ARCHITECTURE, published on Feb. 5, 2004; U.S. Patent Application No. 2001/0024440 to Pounds et al., entitled SYSTEMS AND METHODS FOR MULTIPLE MODE VOICE AND DA TA COMMUNICATIONS HAVING INTELLIGENTLY BRIDGED TDM AND PACKET BUSES AND TELEPHONY STATION CARDS INCLUDING VOLTAGE GENERATIORS, published on Sep. 27, 2001; U.S. Patent Application No. 2003/0012184 to Walker III et al., entitled INTEGRATED ACCESS DEVICE, published on Jan. 16, 2003; U.S. Patent Application No. 2004/0052242 to Laturell, entitled POTS/BROADBAND VOICE CROSS-CONNECT SYSTEM, published on Mar. 18, 2004; U.S. Patent Application No. 2004/0037219 to Shaffer et al., entitled SYSTEM AND METHOD FOR PROVIDING FAULT TOLERANT IP SERVICES, published on Feb. 26, 2004; and U.S. Patent Application No. 2004/0052350 to Jaroker, entitled SYSTEM AND METHOD FOR DELIVERING ENHANCED VOICE AND DATA SERVICES IN PARALLEL WITH AN INCUMBENT PHONE COMPANY, published on Mar. 18, 2004.